Lignin oxidation mechanisms under oxygen delignification conditions. Part 2: Advanced methods for the detailed characterization of lignin oxidation mechanisms

Stella Rovio (Corresponding Author), Susanna Kuitunen, Taina Ohra-aho, Sami Alakurtti, Anna Kalliola, Tarja Tamminen

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19 Citations (Scopus)

Abstract

Advanced analysis methods have been developed to follow the reactions of lignin during alkaline oxygen delignification conditions more comprehensively than before. This aim was attained by monitoring both the lignin macromolecule and the dissolved reaction products. Softwood (SW) and hardwood (HW) kraft spent liquor lignins were studied as substrates under various reaction conditions. The decrease in the contents of different types of free phenolic hydroxyl groups and the concurrent formation of carboxylic acids was followed by 31P NMR of the phosphitylated products. In addition, the formation of acidic degradation products with low molecular weight was determined by capillary zone electrophoresis (CE). This way, it was possible to distinguish the carboxylic acids bound to the lignin macromolecule from the cleaved reaction products, even if they partly co-precipitated during sample preparation. Peak deconvolution was applied to get information on syringyl type phenolic structures and on C(5) condensed guaiacyl structures in hardwood lignin. Pyrolysis-GC/MS was applied to provide additional information about the distribution of guaiacyl/syringyl/p-hydroxyphenyl (G/S/H) type lignin subunits, as well as changes in the phenylpropane side chain.
Original languageEnglish
Pages (from-to)575-585
Number of pages11
JournalHolzforschung
Volume65
Issue number4
DOIs
Publication statusPublished - 2011
MoE publication typeA1 Journal article-refereed
Event11th European Workshop on Lignocellulosics and Pulp, EWLP 2010 - Hamburg, Germany
Duration: 16 Aug 201019 Aug 2010
Conference number: 11

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Keywords

  • Analytical pyrolysis
  • capillary zone electrophoresis
  • hydroxyl group
  • lignin
  • Phosphorous NMR (31P NMR)
  • oxygen delignification
  • Py-GC/MS

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